Traditionally, clinicians and researchers have incorporated surface electromyography (sEMG) as a diagnostic tool for assessing muscle and even central nervous system (CNS) functions. Recently, a switching dynamic model was developed of the sEMG signals generated during a condition in which the mechanical attachment of the spinal dura to the cervical vertebra creates an unstable nonlinear feedback coupling between the biomechanics of the spine and the CNS. The external visual appearance of this instability may include an involuntarily controlled rocking motion of the spine that resembles butterfly swimming. This motion may produce an intensive stimulation of the nervous system. Moreover, an analysis of the sEMG signals generated by this repetitive motion on spinal cord injury patients may show that it produces some regeneration in the central nervous system.
One problem, however, is that the noninvasive sEMG electrodes collect the nervous signals only indirectly and corrupt them with noise. As such, the sEMG signals are sometimes very difficult to analyze.